private Expression GetExpression(ParameterExpression param, ConditionItem item)
{
//属性表达式
LambdaExpression exp = GetPropertyLambdaExpression(item, param);
//如果有特殊类型处理，则进行处理，暂时不关注
foreach (var provider in TransformProviders)
{
if (provider.Match(item, exp.Body.Type))
{
return(GetGroupExpression(param, provider.Transform(item, exp.Body.Type), Expression.AndAlso));
}
}
//常量表达式
var constant = ChangeTypeToExpression(item, exp.Body.Type);
//以判断符或方法连接
return(QueryMethodExpression.Dictionary[item.Method](exp.Body, constant));
}
static private LambdaExpression GetPropertyLambdaExpression(ConditionItem item, ParameterExpression param)
{
//获取每级属性如c.Users.Proiles.UserId
var props = item.Field.Split('.');
Expression propertyAccess = param;
var typeOfProp = typeof(T);
int i = 0;
do
{
PropertyInfo property = typeOfProp.GetProperty(props[i]);
if (property == null)
{
return(null);
}
typeOfProp = property.PropertyType;
propertyAccess = Expression.MakeMemberAccess(propertyAccess, property);
i++;
} while (i < props.Length);
return(Expression.Lambda(propertyAccess, param));
}